Welcome to TechScreen

Welcome to the TechScreen site. This side shall support the exchange of knowledge in the domain of Web Engineering and related aspects. As a side effect, this side is used for research on knowledge management technologies. User can pose challenges in the problem domain and can participate in quizzes. Further a bibliography about arcticles in different related domains is continously extended. Finally, questionnaires on different issues are provided. To be able to participate you need an account and a password from TU Wien's TISS system.

Display pdf document in an more pleasant way

I had an pdf with about 1000 Sites consisting only of tables. To navigate and find something in this Document wasn’t that easy. This leads me to develop a web application that should represent the data in a more pleasant way. First I had to analyze the PDF Document, there are several different pdf versions and standards, the second thing that have to be checks is the structure of the document. For example the document could consists of only pictures, which would make the task harder, since there is no text. In my case the pdf structure was straight forward and consists of text boxes.

Secure private network

To secure the private home network, especially create a guest network and a private one, I used raspberry pi. The private network must be protected better, because of devices like computer, NAS, ect… . The raspberry is equipped with an additional lan port (usb to lan) and an additional w-lan card for a better signal. The first lan port is connected with the router of the ISP and the second one with the local private network. After that the routing is made (IP Tables) so that the internet is forwarded to the private network.

Receive HTTP 500 error after accessing wordpress page

I developed a wordpress website for our company. It has always worked perfectly but today I entered the URL in the browser but I only received the HTTP 500 error message. What can be the reason for this exception when there is nothing changed for months expect updates of the plugins and the theme?

Using joins (mySQL) in a query

Actually in a web application performance has a huge influence on usability. So I often use joins in my queries to provide compact sql queries. But queries with many joins have a bad performance and the user have to wait for a long time. Is there a better opportunity to provide a better performance?

HTTP error code when session token expires

After login to the web site there is a token valid for 15 minutes. In this time you are able to work on the side. After this 15 minutes the session token gets invalid. Which HTTP error code is correct? Actually we are using the 404 error code is this correct?

Performance monitoring of a cloud deployment

An application go-live took a wrong turn - a dozen of connected clients took a cloud system down, that should cope with thousands of them.

Broken caching in a web application

In a Spring Boot Java Web App we had caching set up for several computationally expensive methods. After some time I discovered that the mechanism was apparently broken for those methods, but implementing a new cached method in a completely new service class worked. At first I tried to exclude simple errors as culprits. Method signatures of the cacheable methods were simplified, the @Cacheable method annotation was moved between interface and implementation methods as well as between data repositories and service classes.

Setting up a CI/CD pipeline with centralized logging

An application developed by two engineers began to grow and more developers should be onboarded. What previously worked for two people (simple manual deployment on a webserver and searching through textfile logs when problems arise) wouldn’t work for a bigger team and multiple instances of the product deployed in the cloud. On a mission to cope with that as a new developer in the team I started by simplifying the deployment and packaging the application with a web server into a docker container.

Understanding Floats in CSS

I started programming for about 20 years now. Back in the days CSS was new and very exceiting for me. Coding web pages via the builtin tags to create different visual output (excatly webdesign) was pretty hard, there was a lot of code copy. A little bit later, web pages was built around the 'table' tag, so every webpage was with nested tables, which was extremely hard to manipulate and the overview over the whole document was loose. With CSS (Cascading Style Sheets) everything was new and different, finally you could split code from design and vise verca.

User schooling / training

Everyone learns about simple user interfaces and 'stupid' users. In an online platform with several hundred users, I worked under the assumption that the user interface has to be as clean and simple as possible and the workflow has to be self-explanatory. The problem is, you absolutely cannot imagine the degree of 'creativity' of a user that is not in the field of IT! The platform has some complexity, but the design is well thought out and planned.

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